In current manufacturing engineering, five-axis computer numerically controlled (CNC) machine tools are more and more applied in the processing industry. A five-axis CNC machine tool refers to a CNC machine tool having three orthogonal axes and many swivel shafts, which uses a spindle to rotate a cutting tool to remove material from a workpiece; and then the workpiece can tilt at some angle via the swivel shaft so as to perform tilted plane machining or dynamically reorient the cutting tool to perform complicated multi-axis cutting process. However, since the increase in degrees of freedom accompanies an increase in the complexity of workpiece arrangement and workpiece program, both are significant challenges to conventional machining operations.
The practicality of the five-axis CNC machine tool has a significantly upward trend which can be attributed to two main types of machining applications. The first major application is to manufacture complicated geometrical form that requires precise control on the pose of the tool or workpiece so as to complete the processing of complicated spatial geometrical form. This application usually focuses on complicated curves and the gear is machined in contour paths of various roll angles of the tool shaft. The second major application of five-axis machining is the fabrication of three-axis or four-axis workpieces that require machining on multiple planes, and using a five-axis CNC machine tool can reduce errors and increase efficiency by. Compared to traditional three-axis or four-axis machining, the advantage is that a operator does not have to carry out multiple settings, reset a tool or a workpiece for origin shift, and set up many workpiece programs for each machining process under the limitation from a three-axis or four-axis machine tool. This kind of application is usually referred to as five-axis machining on an inclined plane, the major application requirement of a five-axis CNC machine tool.
Though the above-mentioned five-axis machining on inclined plane is basically the three-axis machining on various workpiece planes, significant differences actually exist in the process flow. As for the five-axis tilted plane machining, additional degree of freedom needs to be controlled, and the type of the machine tool as well as the practical mechanical design are also different. Therefore, complexity over position commands and the relative coordinate system transformations in the machining process shows significant increase.
For example, in the settings of the machining path of the traditional three-axis CNC machine tool, as long as the reference point and the actual working position of the tool are the same, the same program code can be applied in various machine tools and the same machining result is obtained; but when a five-axis CNC machine tool performs machining along the path with tilted planes, transformations of the reference frame is involved and the coordinate system transformations is affected by size or type of the machine itself. Therefore, when the program codes of the same contour path is applied in various machines, different forms by machining are probably obtained and even they cannot be read for machine type.
Therefore, the workpiece programs executed by a five-axis CNC machine tool mostly need additional computer equipments, and are generated by Computer Aided Design (CAD) and Computer-Aided Manufacturing (CAM) software exclusively corresponding to practical application, which are different from the traditional three-axis machine tool. The workpiece program of a three-axis machine tool can usually be programmed directly on the machine tool through manual operation or built-in interactive editor of control system, so that immediately modifying the machining program directly on the machine is difficult for a five-axis CNC machine tool.